17. Lady Grey Dr. behind Royal Canadian Mint
Limestones from a depositional environment of episodic storms
Royal Canadian Mint
Lady Grey Dr. behind Royal Canadian Mint, Ottawa, Ont. The rock outcrop is at the bottom of the sidewalk that ascends the cliff to Sussex Dr.
This outcrop represents a section of the Upper Ordovician Verulam Formation. (This overlies the Hull Formation.) The Verulam Formation documents sedimentation in deeper water than the Hull Formation, but in water depth still influenced by storm activity. The outcrop shows a number of important sedimentary features: (1) fining-upward limestones; (2) erosional boundaries on most beds; (3) lateral truncation and erosion of single beds; (4) alternating coarser and finer grained limestones; (5) rip-up clasts; (6) burrowed tops of beds. These features illustrate a depositional environment influenced by episodic storms that eroded the seafloor (locally lithified = rip-up clasts), then deposited sediment with waning (slowing) flow to produce fining-upward grain sizes. Between storms, the beds were burrowed (forming trace fossils) by organisms that did not leave any skeletal material.